The present invention relates to a demisting control system of an air conditioner installed on automotive vehicles or the like.
A cooling air conditioner has been known, e.g. from Japanese Patent Publication (Kokoku) No. 60-54563, in which air temperature in a space to be cooled is compared with a predetermined cooling start temperature and a predetermined cooling stop temperature, and the operation of a compressor is controlled in an ON- and OFF-manner in accordance with the comparison results, so as to maintain the temperature and humidity in the space within respective predetermined ranges satisfying comfortable conditions. The above-described cooling air conditioner has a control system which is operable such that in order to avoid that the compressor is continuously operated for a long period of time, the compressor is kept operative ("ON" operation) for a first predetermined period of time, and then kept inoperative ("OFF" operation) for a second predetermined period of time immediately following the first predetermined period of time, and thereafter these on and off operations are repeated, to thereby secure comfortableness within the space to be cooled and reduce the power energy consumed by the air conditioner.
When the above conventional control system is employed to remove mist on a window pane of the automotive vehicle, i.e., to demist the window pane, it is necessary to set the aforesaid predetermined cooling start and stop temperatures at respective values equal to or lower than the ambient or outdoor air temperature. The reason for this is that mist occurs on the window pane when cooling operation of the air conditioner is not carried out and when, in general, the outdoor air temperature is lower than the indoor air hr compartment temperature.
Accordingly, demisting of the window pane is carried out by heating the vehicle compartment, or by increasing the heating degree, to prevent the indoor air temperature from being lowered. As a consequence, however, the indoor air temperature does not readily reach the aforesaid predetermined cooling stop temperature. In the meantime, the first predetermined period of time elapses so that the compressor is switched to the "OFF" operation. However, the first predetermined period of time must be set at such a fixed value as to obtain comfortableness of the space to be cooled or vehicle compartment at cooling operation of the air conditioner. Therefore, the operation of the air conditioner in the vicinity of the predetermined cooling start and stop temperatures set at their respective values equal to or lower than the low outdoor air temperature enough not to necessitate cooling operation causes the evaporator to freeze hard by the time the first predetermined period of time elapses, even if the predetermined cooling stop temperature is equal to or above 0 (zero) .degree. C.